What are the best practices for selecting, filtering and sorting "Left Joined" documents in MongoDB?

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Use an indexed field for the join operation: When performing a left join operation, it is crucial to use an indexed field for the join. This will improve the performance of the query and ensure that it runs efficiently.

Filter the joined documents using a pipeline: When performing a left join, it is often necessary to filter the joined documents to narrow down the results. For example, if you want to find all customers who have not made a purchase in the last 30 days, you can use a pipeline to filter the joined documents.

Use $lookup to perform the join operation: MongoDB provides the $lookup operator to perform left join operations. This operator allows you to join documents from multiple collections based on a specified field.

Sort the joined documents using an indexed field: It is often necessary to sort the joined documents to present the results in a meaningful way. When sorting, it is important to use an indexed field to ensure that the query runs quickly.

Use the aggregate framework for complex queries: If you need to perform more complex queries involving left join operations, the MongoDB aggregate framework provides a powerful set of tools to filter, sort, and manipulate data. The framework allows you to perform multiple operations in a single query, reducing the number of roundtrips to the database and improving query performance.